LSI Logic Confidential
8-24
Host Slave Interface
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
0 = System writes the Host DMA transfers
WRData
WRITE Data
0
The value of this bit is written to any selected bits during
Host DMA configuration register writes. Bits to be written
are selected by placing a 1 in each desired location as
the register is written. Any bit positions that contain a 0
during register writes remain unchanged.
Value is written to selected bits.
8.7.2
Host DMA NextAddress Register (CBus Address: 0x60064)
This register at control bus address 0x60064 specifies the SDRAM
address for host DMA data. When GO is set, this register specifies the
starting SDRAM address where host DMA data will be stored or read.
As DMA data is transferred, this register is updated, automatically by
hardware, to point to one byte after the last transferred byte in SDRAM.
This register is read by microcode to determine how many bytes of DMA
information have been transferred. The two least significant and the
upper 4 bits of this register must be zero.
8.7.3
Host DMA StopAddress Register (CBus Address: 0x60068)
This register at control bus address 0x60068 specifies the transfer stop
SDRAM address for host DMA data. When the Next Address reaches the
value in this register and the DMA data has been transferred to SDRAM
or the system, the DMA transfer is completed and the GO bit is cleared.
This register can be reloaded while a DMA transfer is active to extend
the length of a DMA operation. In a normal operation, this register should
never be greater than or equal to the address value stored in the Limit
Address register. The two least significant and the upper 4 bits of this
register must be zero.
While a DMA transfer is active, the Stop Address register should not be
reloaded with the address value of the Next Address register. It is
possible that the Next Address hits the old Stop Address when the Stop
Address Register is reloaded with a new value.
Note:
Reloads of the stop address must be synchronized with
DMA completion detection so that the DMA operation is not
restarted after the GO bit is cleared or a completion
interrupt is generated.
Содержание DMN-8600
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